Polymeric membranes typically possess a broad pore-size distribution that leads to much lower selectivity in molecular and ionic separation when compared to membranes made of crystalline porous materials; however, they are highly desirable because of their easy processability and low cost. Recently, a novel type of conjugated microporous polymers (CMPs) has shown uniform pore size and high porosity. However, their brittleness nature has prevented them from preparing robust membranes and using in pressure-driven membrane processes. In this dissertation, we demonstrate the fabrication of robust polycarbazole-type conjugated microporous polymer membranes using an easy to scale-up electropolymerization strategy. The mechanical properties of the CMP membranes were greatly enhanced based on membrane structure optimization and molecular design. The prepared membranes exhibited high uniform sub-nanometer pores and a precisely tunable membrane thickness and properties, yielding high molecular/ionic sieving performance. In addition, using the co-electropolymerization method, the CMP membranes achieve dual softness and functionalization adjustments. The membrane structure comprises rigid monomers to inherit the structural uniformity and flexible and charged monomers to enhance mechanical flexibility and improve ion selectivity by combining the precise size sieving and the Donnan effect. The dual-adjustments result in the further enhancement of the CMP membranes in ionic sieving performance. Inspired by light-gated ion channels in living cells, we further develop a smart artificial light-gated ion channel membrane. The prepared CMP membranes, based on a conjugated microporous polymer (CMP) functionalized with azobenzene and precisely designed on the molecular level, show uniform pore channels and highly sensitive light-switchable response. The photoisomerization results in reversible geometric changes in pore channel size, leading to “on-off-on” light-control over the channels, which results in light-gated ion transport across the smart membrane. The softness adjustment, functionalization adjustment to CMP membranes, and the design of smart CMP membranes provide potential applications for this important category of polymer materials in the membrane field.
|Date made available
|KAUST Research Repository